This invention relates to an anti-afterburn device for an engine of a vehicle in which secondary air is supplied to an exhaust manifold of the engine for purifying exhaust gas.
In order to purify the exhaust gas, it has been known that secondary air is supplied to thermal reactors or catalytic convertors to reburn positively unburned gas to be discharged from the engine before it is discharged into the atmosphere. In this case, if the exhaust gas containing a large amount of unburned gas is discharged from the engine to the exhaust manifold, it reacts with the secondary air within the reactor or convertor, thereby causing an explosion or afterburn. When a throttle valve of a carburetor is opened or closed rapidly, richer air-fuel mixture is supplied to the engine and not burned completely in a combustion chamber thereof, so that said gas containing the unburned gas is discharged into said exhaust manifold to increase the generation of afterburn.
In conventional technics relating to anti-afterburn, there has been provided devices in which the supply of secondary air is terminated or fresh air is supplied to an intake manifold upon deceleration. However, in these devices, delay of operation thereof is occurred and due to this delay the after-burn is generated by the secondary air supplied before the deceleration.
To this end, we have proposed a device in which the supply of secondary air is interrupted for few seconds just after abrupt acceleration or deceleration to prevent the afterburn of the engine. This device comprises two chambers defined within a housing by a diaphragm by which a spring is positioned substantially perpendicular to a surface of the diaphragm, one of said chambers being connected to a conduit through an orifice and the other being connected directly to another conduit, or each of said chambers being connected to a conduit through an orifice and a check valve, said conduits being connected to an intake manifold, an acceleration sensor operated by a boost pressure in said intake manifold, and an air control valve actuated by an operation of said acceleration sensor and adapted to open and close a secondary air supply conduit for an engine having an air pump, the supply of the secondary air to an exhaust pipe for the engine being interrupted to prevent an afterburn when a throttle valve is opened or closed abruptly.